There are a variety of mechanisms available to connect a towing unit such as a car, truck, or tractor-trailer with a unit desired to be towed, such as campers, boats, other small trailers, livestock trailers, and larger over-the-road trailers. Ball hitches, fifth wheel hitches, and tractor-trailer hitches are some examples of such existing mechanisms.
Regardless of the particular connection between the towing unit and the towed unit, the forces involving in towing frequently result in undesirable motion between the towing unit and the towed unit, including a back-to-back or jarring motion. For example, during acceleration or deceleration, the towing unit and the towed unit may get out of synchronization. That is, one unit may be accelerating at a greater rate than the other, or one unit may be decelerating at a greater rate than the other. This can create a jarring, back and forth motion between the towing unit and the towed unit. Rough roads, turns, and other variables during operation may also cause or increase the frequency, duration and/or extent of such motion.
Prior attempts to reduce, or smooth out, these undesirable forces in towing have not satisfactorily solved these issues. For example, air-ride truck-tractors, trailers with air-ride, and even air-ride cabs have been employed. Although these air-ride type of units may reduce a certain amount of undesirable vertical movement, they do not address the issue of back and forth jarring, which is a predominantly horizontal motion.
One proposed solution suspends a ball hitch of the towing vehicle on a swinging plate movably connected with swinging arms to a plate mounted to the rear of the towing vehicle. See U.S. Pat. No. 5,851,021. In that device, the swinging plate, and therefore the ball hitch itself, move forward and upward relative to the towing vehicle during acceleration, and move rearward and upward relative to the towing vehicle during deceleration. Although the swinging arms also are intended to move upward whether swinging fore or aft, the swinging plate and the ball hitch are intended to remain in constant angular orientation relative to the plate mounted to the rear of the towing vehicle. This device provides some reduction of the undesirable horizontal motion between a towing vehicle and a towed vehicle, but is overly active and lacks sufficient dampening under acceleration and deceleration.
Therefore, a need exists to reduce the amount of jarring between a towing unit and towed unit during operation, and particularly reduce the amount of non-vertical jarring during acceleration and deceleration.